<i>Gaeumannomyces graminis var. triciti (Ggt)</i>, the causal agent of take-all in wheat, is difficult to detect accurately and rapidly due to its similarity to fungi in the Gaeumannomyces-Phialophora complex. My objectives are to detect the fungus in infested plants and soil, and to predict effective combinations of bacteria as biological control agents. Detection was based on avenacinase-based primers and polymerase chain reaction (PCR) conditions specified by earlier research. PCR conditions were modified to effect detection. The annealing temperature was lowered from 68 to 62°C for plant and soil extracts, and the concentration of Taq polymerase was doubled for soil extracts. The lowest detection limit for plant extraction was with plant grown on 4 g Ggt-infested millet seed per kg soil, and that for soil extraction was 16 <span style="font-family:Symbol">m</span>g of purified Ggt DNA per g soil. Chemical and cultural control methods are currently inadequate. Biological control using bacteria is an alternative. Combinations of several bacterial strains are expected to work better than a single strain, but they may be less effective if bacteria antagonize each other or compete for the same rhizosphere habitat. Antagonism of potential biological control agents were assessed using a Petri plate assay. To estimate possible habitat competition, nutritional profiles of the strains were evaluated using the BIOLOG system. I hypothesized that bacteria not antagonistic to each other and having low coefficients of nutritional similarity would make better biological control combinations. Six bacterial combinations gave better mean root weight in the greenhouse experiment but not in the field. / Master of Science

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Denna uppsats syftar till att undersöka hur Riksbankens stora köp av stats- och företagsobligationer hjälpte till att återhämta den svenska ekonomin efter den ekonomiska nedgången år 2020. För att genomföra denna analys nyttjar jag en strukturell vektor autoregressions-modell, samt ett flertal variabler som är väsentliga inom den svenska ekonomin. Den data som används sträcker sig mellan januari 2011 och december 2020. Resultaten visar att Riksbankens obligationsköp först minskade industriproduktionen som sedan återgick till sin normala nivå. Både den långa och den korta räntan påverkades i mycket liten utsträckning. Riksbankens obligationsköp ledde till en uppgång på börsen och en depreciering av den svenska kronan. Slutsatsen utifrån detta är att Riksbankens köp av obligationer bidrog till att stimulera den svenska ekonomin i begränsad utsträckning.

Over the last twenty years or so the Dynamic Volatility literature has produced a wealth of univariate and multivariate GARCH type models. While the univariate models have been relatively successful in empirical studies, they suffer from a number ofweaknesses, such as unverifiable parameter restrictions, existence of moment conditions and the retention of Normality. These problems are naturally more acute in the multivariate GARCH type models, which in addition have the problem of overparameterization. This dissertation uses the Student's t distribution and follows the Probabilistic Reduction (PR) methodology to modify and extend the univariate and multivariate volatility models viewed as alternative to the GARCH models. Its most important advantage is that it gives rise to internally consistent statistical models that do not require ad hoc parameter restrictions unlike the GARCH formulations. Chapters 1 and 2 provide an overview of my dissertation and recent developments in the volatility literature. In Chapter 3 we provide an empirical illustration of the PR approach for modeling univariate volatility. Estimation results suggest that the Student's t AR model is a parsimonious and statistically adequate representation of exchange rate returns and Dow Jones returns data. Econometric modeling based on the Student's t distribution introduces an additional variable - the degree of freedom parameter. In Chapter 4 we focus on two questions relating to the `degree of freedom' parameter. A simulation study is used to examine:(i) the ability of the kurtosis coefficient to accurately capture the implied degrees of freedom, and (ii) the ability of Student's t GARCH model to estimate the true degree of freedom parameter accurately. Simulation results reveal that the kurtosis coefficient and the Student's t GARCH model (Bollerslev, 1987) provide biased and inconsistent estimators of the degree of freedom parameter. Chapter 5 develops the Students' t Dynamic Linear Regression (DLR) }model which allows us to explain univariate volatility in terms of: (i) volatility in the past history of the series itself and (ii) volatility in other relevant exogenous variables. Empirical results of this chapter suggest that the Student's t DLR model provides a promising way to model volatility. The main advantage of this model is that it is defined in terms of observable random variables and their lags, and not the errors as is the case with the GARCH models. This makes the inclusion of relevant exogenous variables a natural part of the model set up. In Chapter 6 we propose the Student's t VAR model which deals effectively with several key issues raised in the multivariate volatility literature. In particular, it ensures positive definiteness of the variance-covariance matrix without requiring any unrealistic coefficient restrictions and provides a parsimonious description of the conditional variance-covariance matrix by jointly modeling the conditional mean and variance functions. / Ph. D.

In large-scale air quality simulations we are interested in the influence factors which cause changes of pollutants, and optimization methods which improve forecasts. The solutions to these problems can be achieved by incorporating adjoint models, which are efficient in computing the derivatives of a functional with respect to a large number of model parameters. In this research we employ first order adjoints in air quality simulations. Moreover, we explore theoretically the computation of second order adjoints for chemical transport models, and illustrate their feasibility in several aspects. We apply first order adjoints to sensitivity analysis and data assimilation. Through sensitivity analysis, we can discover the area that has the largest influence on changes of ozone concentrations at a receptor. For data assimilation with optimization methods which use first order adjoints, we assess their performance under different scenarios. The results indicate that the L-BFGS method is the most efficient. Compared with first order adjoints, second order adjoints have not been used to date in air quality simulation. To explore their utility, we show the construction of second order adjoints for chemical transport models and demonstrate several applications including sensitivity analysis, optimization, uncertainty quantification, and Hessian singular vectors. Since second order adjoints provide second order information in the form of Hessian-vector product instead of the entire Hessian matrix, it is possible to implement applications for large-scale models which require second order derivatives. Finally, we conclude that second order adjoints for chemical transport models are computationally feasible and effective. / Master of Science

EMU as the only functioning single currency area has been criticised as a non-optimal currency area since the Treaty on European Union was signed. Despite this, it has been seen as, probably, the most complete economic project that has ever been conducted by any group of governments. Through Dynamic Factor model and Panel VAR method, we are focusing on the issues of business cycle synchronisation, effectiveness of ECB monetary policy and the euro fiscal dividend, thus to advances the current studies on EMU through assessing whether it can be a sustainable system. For example, whether economic fluctuations can be effectively managed by implementing a single ECB monetary policy and financial market can be relied upon as a monitoring and enforcing device to discipline fiscal behaviour of Eurozone countries. Overall, we concluded that EMU could be more sustainable if it was just formed by its core members, leaving the periphery outside the single currency area. However, since the EU has recently conducted many rescue measures to save the Eurozone, we are unlikely to see those troubled countries to quit EMU, at least, at the present time. The sustainability of the current EMU can be improved if more intra-trade can be promoted to enhance business cycle convergence; hence, it will be more likely to have a union-wide appropriate monetary policy. This will also reduce the requirement of depending upon using fiscal measures to compensate the loss of monetary sovereignty. Moreover, fiscal activities can also be better monitored/enforced since the financial market has begun to adequately adjust the long-term interest rates on Eurozone government bonds according to the development in those countries fiscal stance.

This dissertation is comprised of four chapters. Chapter 1 provides an introduction to<br />Economic application of time series analysis and discusses the topics covered in each of the following chapters along with some main results therein. <br />    In Chapter 2, I construct a measure of information asymmetry in the financial markets in U.S., by estimating an index of agency cost pertaining to U.S. manufacturing firms. The cyclical behavior of the unobservable agency cost is derived by a novel application of the Kalman filter within a Bayesian framework, using firm level data from 1984-2006. The preliminary results provide support to the financial accelerator mechanism in the business cycle literature. <br />    In Chapter 3, I show that people\'s expectation of uncertainty in financial markets is a significant factor impacting short-term real exchange rate movements. Specifically, a sudden increase in expectation of stock market volatility in a low interest rate country tends to appreciate their currencies against high interest rate currencies. I construct a measure of conditional expected uncertainty from volatility of returns of the dominant portfolio (indices) of 7 industrialized countries. I identify uncertainty shocks and its impact on dollar real exchange rate, and explain my results in the context of currency carry trade.<br />    Chapter 4 of my dissertation documents the presence of significant non-linearity in the deficit-interest rate relationship in the U.S. economy. Using an asymptotic threshold test as per Hansen (2000), I find strong evidence for threshold effects in the impact of expected deficit on future long-term interest rates. I find that a percentage point increase in expected deficit in a regime where the expected deficit/GDP ratio is above 1.8 percent (the estimated threshold value) increases future nominal long term interest rates by 29-30 basis point, and a "news shock" to expectation of future deficit increases future real long term interest rates by 12-18 basis points. When expected deficit/GDP ratio is below 1.8 percent, an increase in expected deficit has no impact on future long-term interest rates. <br /> / Ph. D.

This thesis explores the theory and practice of sovereignty. I begin with a conceptual analysis of sovereignty, examining its theological roots in contrast with its later influence in contestations over political authority. Theological debates surrounding God’s sovereignty dealt not with the question of legitimacy, which would become important for political sovereignty, but instead with the limits of his ability. Read as an ontological capacity, sovereignty is coterminous with an existent’s activity in the world. As lived, this capacity is regularly limited by the ways in which space is produced via its representations, its symbols, and its practices. All collective appropriations of space have a nomos that characterizes their practice. Foucault’s account of “biopolitics” provides an account of how contemporary materiality is distributed, an account that can be supplemented by sociological typologies of how city space is typically produced. The collective biopolitical distribution of space expands the range of practices that representationally legibilize activity in the world, thereby expanding the conceptual limits of existents and what it means for them to act up to the borders of their capacity, i.e., to practice sovereignty. The desire for total authorial capacity expresses itself in relations of domination and subordination that never erase the fundamental precarity of subjects, even as these expressions seek to disguise it. I conclude with a close reading of narratives recounting the lives of residents in Chicago’s Englewood, reading their activity as practices of sovereignty which manifest variously as they master and produce space. / Ph. D.

The objectives of this research were: 1) to quantify the amount of supplemental nitrogen (N) to maximize organic broccoli (Brassica olearcea var. italica) on transition soils, 2) to evaluate the ability of leguminous cover crops lablab (Dolichos lablab L.), soybean (Glycine max L.), sunn hemp (Crotalria juncea L.) and a sunn hemp and cowpea mixture (Vigna sinensis Endl.) to supply N and suppress weeds and, 3) to compare the effect on N availability and broccoli yield potential of incorporating cover crops with conventional tillage (CT) or mulching cover crops with no-tillage (NT) practices. Broccoli was grown during the third year of organic transition in the spring and fall of 2006 at the Kentland Agricultural Research Farm in Blacksburg, VA. Supplemental N significantly increased broccoli yield up until 112 kg ha-1 with a quadratic correlation with leaf N. The NT treatment yielded no difference during the spring, but in the fall CT surpassed NT. On the other hand, N uptake, measured by leaf N, under NT conditions increased with supplemental N, which suggests NT has equivalent yield potential as CT when N is not limiting. Yields from leguminous residues did not differ, even though quality and quantity of cover crop biomass did. This suggests that N availability from cover crop legumes may be impacted other ecological process such as soil microbial activity. Also, cover crop residues differed in their ability to suppress weeds. The results from this study give organic growers in transition tools to maximize productivity and sustainability. / Master of Science

Yes / We examine the possible interactions of the financial cycle and fiscal position for G7 economies. We employ the innovative aggregate financial and fiscal stress indexes which are able to depict the perplexed nature of modern economies. A SVAR model is developed to investigate the effects of both financial and fiscal stress on key macroeconomic variables. The results, using two different identification methods, reveal that financial and fiscal shocks affect negatively the key macroeconomic variables. Additionally, there is a weak feedback effect from a financial shock to fiscal sector and vice versa.